Children and adults with chronic renal failure (CRF) develop anemia due to erythropoietin deficiency. Recombinant human erythropoeitin (r-HuEPO) is an effective treatment for most children with the anemia of CRF, however, it requires injections 2-3 times per week in most people. This glycoprotein has been modified in the design of Novel Erythropoiesis Stimulating Protein (NESP) to increase the circulating half life and allow less frequent dosing. Pharmacokinetic studies in adults have shown NESP to have a significantly longer half life than r-HuEPO. The clinical hypotheses of the current study are that 1) the pharmacokinetics of NESP in children are similar to those of previously studied adult CRF patients (NESP 960224) and 2) the safety profile of NESP in children will be similar to that of previously studied adults. The specific aims of this study are: 1) To determine the pharmacokinetics of a single intravenous (IV) bolus dose of NESP in pediatric patients with CRF or ESRD 2) To determine the pharmacokinetics and bioavailability of a single subcutaneous (SC) dose of NESP in pediatric patients with CRF or ESRD 3) To investigate the safety profile of NESP in pediatric patients with CRF or ESRD